Question

a train is moving with a speed of 72km/h takes 20 sec to cross a bridgeof lenght 3 times that of train.the lenght of bridge is

Answer 1

Answer:

Answer is 1200 m

Explanation:

speed =72km/h=20m/s

t=20secs

d=x

d=speed×time

d=20×20=400m

400m here is length of train

3 times 400m is=1200m

Thus,length of bridge is 1200m

Hope it is correct and understandable :)

Answer 2

Given:

• Speed of train = 72 km/hr
• Time taken = 20 seconds
• Bridge is 3 times the length of train.

To find:

• Length of bridge ?

Calculation:

First of all, convert speed unit from km/hr to m/s:

• We know, 1 km/hr = 5/18 m/s

• So, 72 km/hr = 72 × 5/18 = 20 m/s.

Now, the distance covered by the train within this 20 seconds will be equal to the length of the bridge.

$L = v \times t$

$\implies \: L = 20 \times 20$

$\implies \: L = 400 \: metres$

So, length of bridge is 400 metres.

• Please note that : "bridge is 3 times the train length " : THIS STATEMENT IS GIVEN TO CONFUSE YOU !